Yes, I meant "open" in the sense that you do not need to jailbreak it to run software that has not been approved by the manufacturer, not "open" in the sense that the operating system is open source.

Although, I think a lot of their operating system is open source and on their github page (linux kernel and uboot configuration): https://github.com/reMarkable

Their Qt-based shell software, xochitl, is not open source.